The .50 Browning Machine Gun (.50 BMG) or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge.
The cartridge itself has been made in many variants: multiple
generations of regular ball, tracer, armor piercing, incendiary, and
saboted sub-caliber rounds. The rounds intended for machine guns are
linked using metallic links.The .50 BMG cartridge is also used in
long-range target and sniper rifles, as well as other .50 caliber
machine guns. The use in single-shot and semi-automatic rifles has
resulted in many specialized match-grade rounds not used in .50 caliber machine guns.